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c#mathsymbolic-math

The name 'cos' does not exist in the current context

I'm trying to derive using the math.net.symbolics library.

I am getting this error: Compiler Error CS0103 The name 'cos' does not exist in the current context

private void Form1_Load(object sender, EventArgs e)
    {
        var x = Expr.Variable("x");
        var func = 2 * x * x - 2 * Trigonometric.Contract(cos(x)) + 1;     //exc. question: 2 * x * x - 2 * cos(x) + 1
        Console.WriteLine("f(x) = " + func.ToString());                     //answer: //4*x+2*sin(x)     

        var derivative = func.Differentiate(x);
        Console.WriteLine("f'(x) = " + derivative.ToString());
    }
Solution

  • The documentation is for F#. it wasn't working because I was writing code in C#.

    Problem fixed when I used

    x.Cos()

    instead of

    cos(x)